Germanium diode
A germanium diode is a diode based on single crystal germanium . This semiconductor material is doped in such a way that a pn junction is created. Flat diodes , tip diodes and photodiodes were manufactured.
Germanium diodes have a significantly softer characteristic curve kink that starts earlier (at 0.2 V) than silicon diodes (at 0.55 V). Because of this property and in the design as a tip diode, they are also suitable for rectifying very high frequencies, u. a. in detector receivers , but also for demodulation in radars and VHF - receivers . Since modern Schottky diodes made of silicon have all of these properties and in some cases even exceed them, there is no longer any reason to use the heat-sensitive Ge diodes.
Before silicon diodes and transistors caught on, germanium was used to manufacture semiconductor components, as the processing of the rarer germanium was initially better mastered than that of silicon . Germanium semiconductors only tolerate low temperatures compared to silicon (approx. 90 ° C compared to approx. 150… 175 ° C) and have higher reverse currents and temperature drifts .
Today, germanium diodes in the form of tip diodes are sometimes still in demand where a low forward voltage is important and only very small currents below 1 mA flow. Germanium tip diodes can rectify frequencies up to at least 10 GHz.
Germanium photodiodes can be used to detect infrared radiation up to a wavelength of around 1.8 µm.
For areas of application where a low forward voltage is required, silicon-based Schottky diodes are increasingly being used, which have forward voltages similar to germanium diodes, but can withstand higher temperatures.
literature
- Erwin Böhmer, Dietmar Ehrhardt, Wolfgang Oberschelp: Elements of applied electronics: Compendium for training and work . 16th edition. Vieweg + Teubner, 2009, ISBN 978-3-8348-0543-0 .